Guarding the envelope : linking outer membrane integrity to envelope stress signaling in Escherichia coli
(2026)
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- (en) The Rcs phosphorelay is a major envelope stress response in Gram-negative bacteria that is strongly activated by defects in lipopolysaccharide (LPS) assembly, yet how such defects are sensed and transmitted across the envelope remains unclear. The outer membrane lipoprotein RcsF has been proposed to monitor envelope integrity through its transient interaction with the β-barrel assembly machinery (BAM), but the molecular determinants controlling this interaction, and whether its loss is itself sufficient to trigger signaling, remain unresolved. Here, we show in Escherichia coli that BamA conformational state is the molecular variable that governs RcsF engagement and thereby gates Rcs activation. Severe LPS core defects destabilize BamA, alter its conformational behavior, and prevent productive BamA-RcsF interaction, in each case correlating with robust Rcs activation. Mg2+ supplementation restores BamA stability and RcsF engagement even in severely truncated LPS backgrounds, identifying divalent cation-mediated LPS packing as a critical determinant of BamA conformational fitness. Engineered RcsF variants impaired in BamA binding activate Rcs in an otherwise intact envelope, demonstrating that loss of BAM engagement is itself sufficient to trigger signaling. Together, our results identify BamA conformational state as the molecular link between LPS core integrity and envelope stress signaling.
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Harb, R. (2026). Guarding the envelope : linking outer membrane integrity to envelope stress signaling in Escherichia coli. https://hdl.handle.net/2078.5/277551